1. Field of the Invention
This invention relates to an image generation method and image generation device. More specifically, the present invention relates to an image generation method and image generation device that generate two-dimensional images from three-dimensional polygons and textures.
2. Background of the Invention
The surfaces of objects around us often have repeated patterns of complex appearance, and the more complex and fine the appearance or pattern is, the more difficult it is to model it with triangles. One solution technique for this is a texture mapping.
Texture mapping produces highly realistic images with a small number of vertices by overlaying image data read by a scanner, etc. onto the surface of objects.
On the other hand, in a graphic system, an entire three-dimensional image is drawn by breaking up the three-dimensional image into triangles or other polygons (unit figures) and drawing these polygons.
In a graphic system that generates two-dimensional images from such three-dimensional polygons and textures, drawing from near the viewpoint to the far distance is rendered by the texture mapping for ground surfaces, water surfaces, and floors.
When one attempts to render an image by texture mapping, the texture that is mapped onto a shape near the viewpoint becomes greatly stretched, which tends to blur the image and greatly detract from the sense of presence.
One way to avoid this is to use a high-density texture. But this method has the disadvantage of wasting a large quantity of texture memory. Also, one encounters a great decrease in processing speed due to page breaks in texture memory that is constituted with the usual kind of dynamic RAM, because access to an extensive address space is required when doing texture mapping.
Another way to avoid this is to express textures with a combination of recursive affine transforms using fractal compression technology, controlling the depth of the recursive drawing in accordance with the precision required at the time of execution. However, this method has the disadvantage that it needs a large quantity of computation resources for recursive drawing, with not much compression possible for images of low recursiveness.
And with regard to reduction or enlargement of an original image at various rates of reduction, the MIPMAP technique, in which image patterns are rendered with reduced or enlarged textures, is superior in that there is little distortion of the image, and texture mapping can be done at high speed. But a problem with this MIPMAP technique is that shapes near the viewpoint are blurred.